Lee, who finished the 2013 season with 99 tackles and four interceptions, suffered a neck injury in the third quarter of a Dec. 9 game against the Chicago Bears.
After missing the Green Bay game on Dec. 15, Lee eventually returned to practice briefly. Further examinations revealed the torn ligaments, and he couldn't pass medical tests to allow him to play, so he missed the remainder of the season.
He has started individual workouts at Valley Ranch and should participate with his teammates when the offseason programs start in late April.
Lee has missed 18 games in four NFL seasons. He missed one game in 2011 because of a dislocated wrist and played the bulk of the remaining games with a cast. He missed 10 games in 2012 because of a toe injury.
"I think I've had a combination of injuries, like the hamstring would be an injury-prone type of injury," Lee said last month. "I think I've also had some bad luck where I got rolled up in a pile with my toe and I've gotten hit by my own guy in a pile.
"I need to find a way to stay healthy, whether it's finding a way to be stronger and not having the hamstring deal or it's hopefully having a little bit better luck. I need a combination of both going forward."